The present invention relates generally to foldable dish reflectors and, more particularly, to light weight foldable parabolic reflectors for use with radio frequency antenna assemblies and in other applications where portability is important. Such structures are advantageously used in conjunction with ground reception from satellites in mobile and portable communication applications.
In the past, attempts have been made to provide different forms of lightweight foldable or easily transportable antenna structures for a variety of applications. For example, U.S. Pat. No. 3,715,760 shows a collapsible dish structure utilizing a number of petal assemblies circumferentially attached to a base. A set of springs are used to deploy the petal assemblies to open positions upon the severing of a constraining band. This type of structure is typical of reflectors intended for use in space in the absence of gravitational and other forces. It includes no means for structurally fixing the petal assemblies in the open position and no provision for permitting the structure to be easily refolded to its closed position.
U.S. Pat. No. 3,360,798 shows leaf springs used to deploy a collapsible reflector assembly in spacecraft operations. The springs bias the reflector towards the open position. Latching tabs and a retaining band must be used to hold the reflector in the initial closed position with each rib folded in half. This design is not practical for portable, terrestrial applications; the springs do not provide fixed structural integrity in the presence of gravity or winds, and there is no apparent practical way to refold such a structure in the field.
U.S. Pat. No. 4,608,571 discloses a collapsible parabolic reflector wherein the ribs themselves provide a biasing force which opposes the opening of the reflector. This force, however, is only developed when the reflector is almost completely open and it does not hold the reflector in either an open or closed position. The great number of mechanical elements and couplings in this complex mechanical design tend to make it impractical for applications where easy use, simplicity and reliability are important.
Finally, in a different field, U.S. Pat. No. 2,113,118 discloses a tent with a foldable framework. A series of springs are attached between adjacent arms which are attached to a central hub. In both closed and open positions, the springs act to pull the arms together, with arms above the hub when closed and below the hub when opened. While the weight of the fabric and side supports is adequate to force the legs downward in the open position, the springs are needed to force the hub above the arms. Thus the arms must be rotated open to a position extending down from the hub to avoid a dished configuration which would defeat the whole purpose of the tent by collecting a pool of water in the rain. In view of the differences in objectives and desired operation, the mechanism of this patent is not relevant to reflectors of the type under discussion.
It is an object of this invention to provide light weight parabolic reflectors which are readily transportable and are adapted for ease of opening and closing in field operations, and which may include elastic biased control of rib opening and closing and fixed restraint of ribs in the open position.
It is a further object to provide foldable reflectors which are both simple in form and reliable in spite of repeated openings and closings in the field, and which permit later readjustments of reflector contours by individual rib angle adjustments.
Yet another object of the invention is to provide a foldable reflector having flexible reflective material comprised of individual, replaceable, sector shaped panels which are attached to and extend between adjacent ribs.